Any danger from these ports?

[Alexander Dalloz]

Am Mi, den 12.01.2005 schrieb Charles R. Anderson um 17:03:

> Passive FTP listens on random local ephemeral ports for data
> connections set up by the 21/tcp control stream.  If you are not using
> a stateful firewall with a FTP helper, then you need to allow incoming
> TCP connections to whatever range your FTP server uses for passive FTP
> (defaults to the entire local port range).  This is why I have always
> set up my FTP server similar to this (older box using ipchains):
> 
> /etc/sysctl.conf:
> net.ipv4.ip_local_port_range = 60000 65535
> 
> /etc/vsftpd.conf:
> pasv_min_port=59000
> pasv_max_port=59999
> 
> /etc/sysconfig/ipchains:
> -A input -i eth0 -s 0.0.0.0/0.0.0.0 -d 0.0.0.0/0.0.0.0 21:21 -p 6 -j ACCEPT
> -A input -i eth0 -s 0.0.0.0/0.0.0.0 -d 0.0.0.0/0.0.0.0 0:58999 -p 6 -l -j DENY
> -A input -i eth0 -s 0.0.0.0/0.0.0.0 -d 0.0.0.0/0.0.0.0 59000:59999 -p 6 -j ACCEPT
> -A input -i eth0 -s 0.0.0.0/0.0.0.0 -d 0.0.0.0/0.0.0.0 60000:65535 -p 6 -y -l -j DENY

It is much better to use ip_conntrack_ftp iptables helper module and the
stateful capabilities of iptables (ESTABLISHED,RELATED) rather than to
"blindly" open a range of high ports. Why using ipchains, which is not
stateful, when having iptables?
Easily be done with the default Fedora Core iptables rules by adding
ip_conntrack_ftp into IPTABLES_MODULES="" in
/etc/sysconfig/iptables-config.

Alexander


-- 
Alexander Dalloz | Enger, Germany | new address - new key: 0xB366A773
legal statement: http://www.uni-x.org/legal.html
Fedora GNU/Linux Core 2 (Tettnang) on Athlon kernel 2.6.10-1.8_FC2smp 
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